CH. XXVIII.] 



MILK. 



457 



In tabular form the facts just given may be more succinctly 

 stated : 



We shall have to return to the composition of diets again in 

 our study of metabolism ; and now we will proceed to consider 

 the principal foods. 



Milk. 



Milk, which we have already spoken of as a perfect food, is 

 only so for young children. For those who are older, it is so 

 voluminous that unpleas- 

 antly large quantities of it 

 would have to be taken in 

 the course of the day to 

 ensure the proper supply 

 of nitrogen and carbon. 

 Moreover, it is relatively 

 too rich in proteid and fat. 

 It also contains too little 

 iron (Bunge) : hence chil- 

 dren weaned late become 

 anaemic. 



The microscope reveals 

 that it consists of two 

 parts : a clear fluid and a Fig. 388. -Globules of cow's milk, x 400. 

 number of minute particles . 



that float in it. These consist of minute oil globules, varying in 

 diameter from 0*0015 to 0^005 millimetre (fig. 388). 



The milk secreted during the first few days of lactation is 

 called colostrum. It contains very little caseinogen, but large 



